Libreoffice Calc Charts: altering data Series range value

Linux Ubuntu 14.04
Version: 1:4.2.8-0ubuntu2)

I have a problem altering data series range value. I have marked the full table as Data Range. Using Line Chart - having two data series (Line 1 and Line 2). X-axis is just time, Y-axis - are values for Line 1 and Line 2. Now as the data is rather enormous I can´t plot out change for every 100 year. So I need to trim it down to make it more readable. But I still need to image the time period of 100 years. My vision would be to set Line 1 and Line 2 Data values on X per every 5 years: 20 values for each. But when I try to use CTRL or Shift to pick for Line 1 and Line 2 X-axis values I can pick only range not single values like 1, 5,15, 20th value on the list. I remember having done this years ago, but somehow no shift, nor CTRL nor both let me pick that way anymore? I know the semicolon trick, but this is as well time consuming, regarding if data tends to grow.

I can get my work done by altering the table and deleting the values in between, but for future I would hope to get this done faster? Can anyone point out what am I missing, doing wrong? As I do not thing the problem is slightly older version here?

Don’t you think you should supply a relevant example? I will see for your “karma” growing high enough.
Please explain very clearly how -and for what reason- you “…marked the full table as Data Range”. You surely didn’t define it as the data range of the chart?
Please make clear if you actually do not expect the “time axis” to be a coordinate axis in the technical sense. Only x-y (“scatter”) charts have a scale in that sense. A line chart only can show the contents of a label range “as x”.

what about adding some temporary rows / columns with ‘reduced’ copies or condensed calculations of the data and creating the chart from that?